海相页岩气储层评价发展趋势与综合评价体系

目前,我国页岩气勘探开发中还存在着储层有效性评价体系不完善、储层评价体系不能满足页岩气高效开发需要等问题。为了完善储层评价内容与标准,基于现有的页岩气储层评价方法,分析页岩气储层静态评价的不足及其面临的挑战,建立了页岩气储层有效性评价方法和孔隙系统划分方案;在此基础上,探讨了页岩压后动态评价参数及其对排采措施的影响,研究了"自动缓解水锁"潜力评价参数,建立了"静—动"结合的储层综合评价体系。研究结果表明:①页岩气储层评价的新挑战表现为"储层有效性、压后动态评价参数体系、压后排采措施"研究不够深入,导致现有的页岩气储层评价体系相对于生产具有严重的滞后性;②储层有效性评价主要表现为有效孔隙度下限评价,体现在黏土矿物束缚水和不连通孔隙对页岩气开发的影响;③页岩气储层评价发展趋势表现为细化储层静态评价参数、建立"自动缓解水锁"潜力评价指标和"静—动"结合的储层综合评价体系;④确定了"润湿性、吸水滞留能力、吸水膨胀方式、膨胀率和吸水产生裂缝能力"等"自动缓解水锁"潜力评价指标的压后动态评价体系;⑤提出了"页岩气储层静态评价是基础,压后动态评价是补充"的储层评价思路,并建立了一套适合我国海相页岩气储层评价的"静—动"结合的储层综合评价体系。

Development trend of marine shale gas reservoir evaluation and a suitable comprehensive evaluation system

At present, shale gas exploration and development in China is faced with some problems, such as the imperfect evaluation system of reservoir effectiveness and the limitations of reservoir evaluation system on efficient development of shale gas. In order to improve the content and the standard of reservoir evaluation, this paper analyzed the shortcomings and challenges in the static evaluation of shale gas reservoirs on the basis of existing reservoir evaluation, and established a method for evaluating shale gas reservoir effectiveness and a scheme for classifying pore systems. Then, the dynamic evaluation parameters after shale fracturing and their effects on drainage and production measures were discussed. In addition, the potential evaluation parameters of "automatic mitigating water blocking" were studied, and a comprehensive reservoir evaluation system of "static–dynamic" combination was established. And the following research results were obtained. First, new challenges to the shale gas reservoir evaluation are emerged as the lack of in-depth study on "reservoir effectiveness, dynamic evaluation parameter system after fracturing and drainage and production measures after fracturing", which leads to the serious lag of existing shale gas reservoir evaluation system behind production. Second, The evaluation of reservoir effectiveness is mainly presented as the evaluation on the lower limit of effective porosity, and is embodied in the influence of clay bound water and unconnected pores on the development of shale gas. Third, the development of shale gas reservoir evaluation follows the trend of refining the static reservoir evaluation parameters, defining the potential evaluation indexes of "automatic mitigating water blocking" and establishing the reservoir comprehensive evaluation system of "static–dynamic" combination. Fourth, a postfrac dynamic evaluation system is determined for the potential evaluation indexes of "automatic mitigating water blocking" (e.g. wettability, water imbibition retention capacity, water imbibition expansion mode, expansion rate, and water imbibition cracking capacity). Fifth, a reservoir evaluation idea is put forward that "static evaluation of shale gas reservoir is the foundation and postfrac dynamic evaluation is the complement", and a comprehensive reservoir evaluation system is established of "static–dynamic" combination suitable for the evaluation of marine shale gas reservoirs in China.